1. Field of the Invention
The invention is concerned with a flexible, adhesive-backed film composite that has an adhesive layer by which it can become permanently bonded to substrates containing migratable monomeric plasticizers, in spite of the tendency of such plasticizers to migrate into and to soften the adhesive. The invention is particularly concerned with the adhesive layer of such a film composite.
2. Description of the Related Art
As is pointed out in U.S. Pat. No. 4,605,592 (Paquette et al.), highly plasticized vinyl substrates previously had been decorated by hand painting or air brushing screen-printing inks. While prefabricated graphics in the form of adhesive-backed vinyl film bearing screen-printed graphics would have been less expensive, they had not been adapted for such use "due to the wrinkling of the vinyl film and loss of adhesion to the vinyl substrate ... attributable, at least in part, to the migration of monomeric plasticizers from the vinyl substrate into the vinyl film and adhesive" (col. 1, lines 24-33). These vinyl substrates contain as much as 25-100 parts of monomeric plasticizer, usually dioctylphthalate, to 100 parts of vinyl resin.
In general, low-cost monomeric plasticizers are more migratory than are those of higher cost, so that attempts by manufacturers of plasticized substrates to economize often exacerbate the problem of adhering a decorative, adhesive-backed flexible film to those substrates.
The Paquette patent provides a composite decorative, article that is capable of maintaining adhesion and remaining substantially wrinkle free when adhered to vinyl substrates that contain migratable monomeric plasticizer. The decorative film composite of the Paquette patent has (1) a polyvinyl chloride film layer that preferably is receptive to screen printing inks, (2) a layer of a plasticizer-resistant pressure-sensitive adhesive, e.g., a terpolymer of by weight 52.5 parts of n-butylacrylate, 37.5 parts methyl acrylate, and 10 parts acrylic acid, and (3) an intermediate, migratable-plasticizer barrier layer such as an aliphatic polyurethane resin. After being coated and dried, the adhesive can be crosslinked, e.g., by exposure to UV radiation when it contains a photocrosslinker such as benzophenone, thus making the adhesive layer more resistant to any plasticizer that migrates from a vinyl substrate. The pressure-sensitive adhesives of the examples of the Paquette patent are polymerized in solution and coated from solution.